Method for controlling the orientation of a solar module with two photoactive faces

ABSTRACT

A method for controlling the orientation of a solar module including a single-axis solar tracker orientable about an axis of rotation, and a photovoltaic device supported by said tracker and having upper and lower photoactive faces, including: measurement of a distribution of the solar luminance called incident luminance originating from the incident solar radiation coming from the sky to reach the upper face, said distribution being established according to several elevation angles; measurement of a distribution of the solar luminance called reflected luminance originating from the albedo solar radiation corresponding to the reflection of the solar radiation on the ground to reach the lower face, said distribution being established according to several elevation angles; determination of an optimum orientation considering the measurements of said distributions of the incident and reflected solar luminance; servo-control of the orientation of the module on said optimum orientation.

The present invention relates to a method for controlling theorientation of a solar module comprising:

-   -   a single-axis solar tracker orientable about an axis of rotation        for an orientation of the solar module allowing following the        Sun during its rise and its descent from east to west; and    -   a photovoltaic device supported by the solar tracker and having        a photoactive upper face facing the sky and provided with        photovoltaic cells and a photoactive lower face facing the        ground and provided with photovoltaic cells.

Thus, the invention falls within the technical field of solar modulesorientable about an axis of rotation and including a photovoltaic deviceof the dual-face technology, that is to say with a productive upper facefacing the Sun and a lower face, also productive, facing the ground. Theupper face benefits from the solar radiation called incident radiation,which corresponds to the direct and/or diffuse solar radiation whichcomes from the sky, whereas the lower face benefits from the solarradiation reflected by the ground, generally called albedo radiation.

It is common to servo-control the orientation of the solar tracker on anorientation called direct orientation based on an astronomicalcalculation of the position of the Sun, for a real-time positioningfacing the Sun.

However, a servo-control on such a direct orientation has a majordrawback by offering a yield deficit under certain weather conditions,and in particular under cloudy conditions which are at the origin of adiffuse solar radiation. The diffuse solar radiation arises when thedirect solar radiation is dispersed in the clouds and the atmosphericparticles. The diffuse solar radiation results from the diffraction oflight by the clouds and by the various molecules in suspension in theatmosphere. Hence, the diffuse solar radiation does not necessarilyfollow the direction defined by the Sun in the direction of theobservation point at the Earth's surface.

Furthermore, with a dual-face technology photovoltaic device,orientating the solar tracker on a direct orientation will notnecessarily lead to a maximum energy yield on the lower face of thephotovoltaic device, depending on the albedo.

The present invention aims at solving these drawbacks by proposing acontrolling method which allows servo-controlling the solar module on anoptimum orientation which will take into account at the same time thedirect radiation, the diffuse radiation and the albedo radiation.

To this end, it proposes a method for controlling the orientation of asolar module comprising:

-   -   a single-axis solar tracker orientable about an axis of rotation        for an orientation of the solar module allowing following the        Sun during its rise and its descent from east to west; and    -   a photovoltaic device supported by said solar tracker and having        a photoactive upper face facing the sky and provided with        photovoltaic cells and a photoactive lower face facing the        ground and provided with photovoltaic cells;

this method comprising the following successive steps:

-   -   measurement of a distribution of the solar luminance called        incident luminance originating from the solar radiation called        incident radiation which comes from the sky and which is capable        of reaching the upper face of the photovoltaic device, said        distribution of the incident solar luminance being established        according to several elevation angles corresponding to several        orientations of the solar module about the axis of rotation;    -   measurement of a distribution of the solar luminance called        reflected luminance originating from the solar radiation called        albedo radiation which corresponds to the reflection of the        solar radiation on the ground and which is capable of reaching        the lower face of the photovoltaic device, said distribution of        the reflected solar luminance being established according to        several elevation angles corresponding to several orientations        of the solar module about the axis of rotation;    -   determination of an optimum orientation of the solar module        considering the measurements of the distribution of the incident        solar luminance and of the distribution of the reflected solar        luminance;    -   servo-control of the orientation of the solar module on said        optimum orientation.

Thus, the method implements a servo-control on an optimum orientationwhich not only takes into account the direct solar radiation, but alsotakes into account the diffuse solar radiation and the albedo radiation,so that the energy production of the upper face of the photovoltaicdevice resulting from both the direct radiation and the diffuseradiation, as well as the energy production of the lower face of thephotovoltaic device resulting from the albedo radiation, will be takeinto consideration.

According to one feature, the controlling method comprises the followingsteps:

-   -   memorization of the past measurements of the distribution of the        incident solar luminance and of the distribution of the        reflected solar luminance;    -   memorization of the past optimum orientations determined for the        past measurements of the distribution of the incident solar        luminance and of the distribution of the reflected solar        luminance;    -   forecast of the future evolutions of the distribution of the        incident solar luminance and of the distribution of the        reflected solar luminance, on the basis of the past measurements        of the distribution of the incident solar luminance and of the        distribution of the reflected solar luminance;    -   calculation of the future evolution of the optimum orientation        according to the forecast of the future evolutions of the        distribution of the incident solar luminance and of the        distribution of the reflected solar luminance;    -   servo-control of the orientation of the solar module on the        optimum orientation according to the past optimum orientations        and according to the future evolution of the optimum        orientation.

Thus, a forecast of the future evolution of the optimum orientation,within a more or less short term, is implemented and, afterwards,according to this future evolution of the optimum orientation, aservo-control of the orientation of the solar module may be proactivelyimplemented, without directly following in real-time the calculatedoptimum orientation, thereby allowing avoiding orientation changes thatwould procure only but little energy gain, and even energy losses, aswould be the case for example if one single cloud passes in front of theSun for a short time period.

According to another feature, the forecast of the future evolutions ofthe distribution of the incident solar luminance and of the distributionof the reflected solar luminance is based on a weather forecastcalculation in a location area of the solar module.

According to a possibility of the invention, the determination of theoptimum orientation of the solar module is based at least partially on aresearch, in the distribution of the incident solar luminance and in thedistribution of the reflected solar luminance, of an elevation angleassociated to a maximum solar illuminance on the two faces of the twofaces of the photovoltaic device.

According to another possibility of the invention, the determination ofthe optimum orientation of the solar module is based at least partiallyon a research, in the distribution of the incident solar luminance andin the distribution of the reflected solar luminance, of an elevationangle associated to a maximum energy production of the solar module.

In a particular embodiment, the determination of the optimum orientationof the solar tracker is also based on the consideration of at least oneof the following parameters:

-   -   an electrical energy consumption necessary to modify the        orientation of the solar module;    -   a wear rate of mechanical members of the solar tracker loaded        during a change of the orientation of the solar module;    -   an angular speed of the solar tracker during a change of the        orientation of the solar module;    -   an angular displacement of the solar tracker between a minimum        orientation and a maximum orientation.

Thus, when servo-controlling on an optimum orientation, the mechanicaland kinematic constraints of the solar tracker are taken intoconsideration so that the servo-control does not become more damagingthan beneficial.

Advantageously, when measuring the distribution of the incident solarluminance, is implemented a frequency weighting dependent of a frequencyresponse of the photovoltaic cells of the upper face of the photovoltaicdevice; and when measuring the distribution of the reflected solarluminance, is implemented a frequency weighting dependent of a frequencyresponse of the photovoltaic cells of the lower face of the photovoltaicdevice.

Thus, these frequency weightings will consist in applying frequencyfilters specific to each face which will take into account the spectralresponse of each face, to the extent that the spectral response of eachface depends on the length of the light radiation received depending onits technology; the spectral response may vary between the two faces ifthese two faces are not of the same technology.

In a particular embodiment, at the step of determining an optimumorientation, the following steps are implemented:

-   -   conversion of the measurement of the distribution of the        incident solar luminance into an incident luminance mapping        defining a distribution of luminance values according to strips        called upper strips, established according to a horizontal first        direction parallel to the axis of rotation, and according to        columns called upper columns, established according to a        horizontal second direction orthogonal to the first direction,        where each upper strip is associated to an elevation angle and        each upper column is associated to an azimuth angle;    -   conversion of the measurement of the distribution of the        reflected solar luminance into a reflected luminance mapping        defining a distribution of luminance values according to strips        called lower strips, established according to the first        direction, and according to columns called lower columns,        established according to the second direction, where each lower        strip is associated to an elevation angle and each lower column        is associated to an azimuth angle;    -   calculation, for each upper and lower strip, of an equivalent        luminance value from the set of luminance values taken in the        considered strip;    -   calculation, for several theoretical elevation angles        corresponding to several orientations of the solar module, of        values of the luminance perceived by the two faces of the        photovoltaic device from the equivalent luminance values        calculated for all the strips and from the angular differences        between the theoretical elevation angles and the elevation        angles associated to the strips;    -   determination of a theoretical elevation angle associated to a        maximum of the perceived luminance value and selection of said        theoretical elevation angle as the optimum orientation.

In this manner, the calculation of the optimum orientation is based onthe calculation of the perceived luminance values associated todifferent elevation angles which are to be matched with the orientationof the solar module. The smaller is the angular difference between thestrips and the higher is the number of strips, the more the calculationof the optimum orientation will be fine and accurate.

In a first embodiment, the measurements of the distribution of theincident solar luminance and of the distribution of the reflected solarluminance are carried out by means of an image capturing device whichensures, on the one hand, a capture of images of the sky for measuringthe distribution of the incident solar luminance and, on the other hand,a capture of images of the ground for establishing the measurement ofthe distribution of the reflected solar luminance.

With an image capture, the distributions of the incident and reflectedsolar luminances are measured from images which will afterwards beconverted into luminance mappings.

In a second embodiment, the measurements of the distribution of theincident solar luminance and of the distribution of the reflected solarluminance are carried out by means of a measuring system comprisingseveral photosensitive sensors, in particular pyranometric-type sensors,with, on the one hand, an upper measuring device having upperphotosensitive sensors distributed facing the sky for measuring thedistribution of the incident solar luminance and, on the other hand, alower measuring device having lower photosensitive sensors distributedfacing the ground for measuring the distribution of the reflected solarluminance.

With a measurement of the solar luminance by photosensitive sensors, thedistributions of the incident and reflected solar luminances aremeasured from matrices of the measurements performed individually byeach photosensitive sensor, these photosensitive sensors beingpositioned at different elevation angles (on the top and on the bottom),and in particular distributed over a sphere-shaped support, in order tooffer a wide observation of the sky and of the ground.

According to a possibility of the invention, the step ofservo-controlling the orientation of the solar module is carried outaccording to the energy consumption necessary to modify the orientationof the solar module.

In other words, the actual servo-control takes into account this energyconsumption in order to implement, or not, an orientation according tothe optimum orientation, so as to anticipate a change in the cloudcoverage.

In accordance with another feature of the invention, at the step ofservo-controlling the orientation of the solar module, is established apotential scenario during which the orientation of the solar module ismodified starting from a current orientation until reaching the optimumorientation, and to this potential scenario are associated thecalculations of:

-   -   an evolution of the orientation of the solar module during the        orientation change starting from the current orientation until        reaching the optimum orientation, this evolution depending on        the rotational displacement speed of the solar module;    -   an evolution of the energy consumption necessary to modify the        orientation of the solar module;    -   an evolution of the supplemental solar energy production        expected with such an orientation change;    -   an evolution of the expected energy yield based on the        difference between the solar energy production and the energy        consumption;

and afterwards, the orientation of the solar module is servo-controlledon said optimum orientation if the energy yield is globally positive forthe scenario, otherwise the orientation of the solar tracker ismaintained at the current orientation.

Thus, the servo-control according to an optimum orientation will not beperformed unless an energy gain is obtained, in order not to implement asystematic orientation change at each change in the cloud coverage.

The invention also relates to a solar module comprising:

-   -   a single-axis solar tracker orientable about an axis of rotation        for an orientation of the solar module allowing tracking the Sun        during its rise and its descent from east to west, said solar        tracker being actuatable in rotation about said axis of rotation        by means of an actuation system;    -   a photovoltaic device supported by said solar tracker and having        a photoactive upper face facing the sky and provided with        photovoltaic cells and a photoactive lower face facing the        ground and provided with photovoltaic cells;

this solar module being remarkable in that it further comprises:

-   -   an upper measuring device capable of measuring a distribution of        the incident solar luminance originating from the incident solar        radiation which comes from the sky and which is capable of        reaching the upper face of the photovoltaic device, said        distribution of the incident solar luminance being established        according to several elevation angles corresponding to several        orientations of the solar module about the axis of rotation;    -   a lower measuring device capable of measuring a distribution of        the reflected solar luminance originating from the albedo solar        radiation which corresponds to the reflection of the solar        radiation on the ground and which is capable of reaching the        lower face of the photovoltaic device, said distribution of the        reflected solar luminance being established according to several        elevation angles corresponding to several orientations of the        solar module about the axis of rotation; and    -   a control unit connected, on the one hand, to the upper and        lower measuring devices and, on the other hand, to the actuation        system for controlling the rotation of the solar tracker, where        said control unit is configured to implement the steps of the        controlling method in accordance with the invention.

Other features and advantages of the present invention will appear uponreading the detailed description hereinafter, of non-limiting examplesof implementation, made with reference to the appended figures in which:

FIG. 1 comprises four diagrams each illustrating a solar module undercloudy (diagrams (a) and (b)) and clear (diagrams (c) and (d)) weatherconditions;

FIG. 2 is a schematic view of a solar module with a single-axis solartracker in accordance with the invention, with an illustration of ameasuring system capable of measuring a distribution of the incidentsolar luminance and a distribution of the reflected solar luminance;

FIGS. 3a are schematic perspective (FIG. 3a ) and vertical sectional(FIG. 3b ) views of a first example of a measuring system;

FIG. 4 is a schematic perspective view of a second example of ameasuring system;

FIG. 5 is a schematic representation of an incident luminance mapping(at the top-left) and of a matrix of equivalent luminance values (at thetop-right) derived from this incident luminance mapping, and of areflected luminance mapping (at the bottom-left) and of a matrix ofequivalent luminance values (at the bottom-right) derived from thisreflected luminance mapping;

FIG. 6 comprises two diagrams, with:

-   -   at the left side, a schematic side view of four upper columns        and four lower columns respectively of incident and reflected        solar luminance mappings, with the azimuth angles associated to        the different columns, in order to illustrate the calculation        implemented for the calculation of an equivalent luminance value        serving to determine the optimum orientation;    -   at the right side, a schematic side view of four upper strips        and four lower strips respectively of incident and reflected        solar luminance mappings, with the elevation angles associated        to the different strips, in order to illustrate the calculation        implemented for the calculation of a perceived luminance value        serving to determine the optimum orientation;

FIG. 7 represents three pairs of incident and reflected solar luminancemappings, to which are associated below the corresponding optimumorientations, including a pair of mappings at a current time point (t)and two pairs of predictive mappings at future time points (t+1) and(t+n);

FIG. 8 is a representation in the form of a block diagram of thefunctional elements used for the implementation of a controlling methodin accordance with the invention;

FIG. 9 represents five predictive curves calculated for a firstpotential scenario defined at the servo-control step, including, fromtop to bottom, a curve of the evolution of the future (or predictive)optimum orientation calculated at the forecasting step, a curve of theevolution of the orientation of the solar module, a curve of theevolution of the energy consumption necessary to modify the orientationof the solar module, a curve of the evolution of the expectedsupplemental solar energy production, and a curve of the evolution ofthe expected energy yield; and

FIG. 10 represents five predictive curves (identical to those of FIG. 9)calculated for a second potential scenario.

Referring to FIG. 2, a solar module 1 comprises:

-   -   a single-axis solar tracker 2 orientable about an axis of        rotation A for an orientation of the solar module 1 allowing        tracking the Sun during its rise and its descent from east to        west; and    -   a photovoltaic device 3 supported by the solar tracker 1 and        having a photoactive upper face 31 facing the sky and provided        with photovoltaic cells and a photoactive lower face 32 facing        the ground and provided with photovoltaic cells.

The solar tracker 2 comprises a fixed structure 21 for anchorage to theground, for example constituted by one or several pylon(s) anchored tothe ground, for example by pile driving, screwing, bolting, ballasting,or any other equivalent means allowing fastening and stabilizing thefixed structure 21 to the ground. The solar tracker 2 further comprisesa movable platform 22 rotatably mounted on the fixed structure 21 aboutthe axis of rotation A, and more specifically rotatably mounted on theupper ends of the pylon(s). This platform 22 supports the photovoltaicdevice 3 which is composed by one or several dual-face technologyphotovoltaic panel(s).

Referring to FIGS. 2 and 6, the axis of rotation A is substantiallyhorizontal and directed according to a longitudinal axis X according tothe north-south direction. When the solar module 1 is flat down (asshown in FIGS. 2 and 6), the faces 31, 32 of the photovoltaic device 3extend according to a horizontal plane defined by the longitudinal axisX and by a transverse axis Y according to the east-west direction,orthogonally to a vertical axis Z.

In the following description, the orientation of the solar module 1(also called orientation or inclination angle of the solar tracker 2 orof the photovoltaic device 3) corresponds to the angle of the normal tothe upper face 31 with respect to the vertical axis Z considered in theplane (Y, Z). Thus, when the solar module 1 is flat down, thisorientation is 0 degree.

The solar module 1 also comprises a measuring system 5 capable ofmeasuring a distribution of the incident solar luminance and adistribution of the reflected solar luminance. This measuring system 5may be associated to one single solar module 1 or, in an economicalmanner, be shared with several solar modules. The measuring system 5 isfixed, and may be raised with respect to the ground, for example bybeing mounted on a post 50.

This measuring system 5 comprises two measuring devices 51, 52, namely:

-   -   an upper measuring device 51 capable of measuring a distribution        of the incident solar luminance originating from the solar        radiation called incident radiation (direct solar radiation Rdir        and diffuse solar radiation Rdif) which comes from the sky and        which is capable of reaching the upper face 31 of the        photovoltaic device 3; and    -   a lower measuring device 52 capable of measuring a distribution        of the reflected solar luminance originating from the albedo        solar radiation Ralb which corresponds to the reflection of the        solar radiation on the ground and which is capable of reaching        the lower face 32 of the photovoltaic device 3.

These two measuring devices 51, 52 may be separated or assembledtogether, as in the example of FIG. 2. With these measuring devices 51,52, each distribution of the concerned (incident or reflected) solarluminance is established according to several elevation angles (anglemeasured with respect to the vertical axis Z in a vertical planeparallel to the longitudinal axis X) corresponding to severalorientations of the solar module 1 about the axis of rotation A. Inother words, these elevation angles are to be matched with theorientations of the solar module 1.

The solar module 1 further comprises an actuation system (notillustrated in FIG. 2 and bearing the reference number 6 in FIG. 10)which ensures rotating the platform 22 about the axis of rotation A.

This actuation system 6 comprises an actuator, for example of the(electric, pneumatic or hydraulic) cylinder type or of the electricmotor (for example rotary motor) type. This actuation system 6 furthercomprises a mechanical system for transmitting the movement at theoutput of the actuator (a rotational movement for a rotary motor, or alinear movement for a cylinder) into a rotational movement of theplatform 22. As a non-limiting example, this mechanical transmissionsystem may be a deformable-parallelogram system, a pulley system, apinion system, a chain system, a belt system, a clutch system, atransmission shaft system, a connecting rod system, etc.

It is possible to consider that the actuator is specific to the solarmodule 1, or is shared between several solar modules. In the case wherethe actuator is shared, the platforms 22 of the different solar trackersare advantageously coupled in rotation, for a synchronous rotation underthe effect of the common actuator.

Referring to FIG. 8, the solar module 1 also comprises a control unit 4such as an electronic board, which is linked to the observation system 5in order to receive its observations (or observations data) and which isalso linked to the actuation system 6 in order to pilot its operationand thus accordingly pilot the rotation of the platform 22, in otherwords the orientation of the solar module 1.

This control unit 4 comprises several modules, namely:

-   -   a cartographic module 40 provided to convert the measurement        performed by the upper measuring device 51 into an incident        luminance mapping CLI, and to convert the measurement performed        by the lower measuring device 52 into a reflected luminance        mapping CLR, and to associate to each luminance mapping CLI, CLR        a time point t;    -   an archiving module 41 which archives each luminance mapping        CLI, CLR generated by the cartographic module 40;    -   a predictive calculation module 42 which calculates a future        evolution of the distribution of the incident solar luminance        and of the distribution of the reflected solar luminance (based        on a weather forecast calculation), and more specifically        calculates predictive incident luminance mappings CLIP and        predictive reflected luminance mappings CLRP for future time        points, this predictive calculation module 42 carrying out these        calculations on the basis of the luminance mappings CLI, CLR        generated in real-time by the cartographic module 40 and on the        basis of the past luminance mappings CLI, CLR archived in the        archiving module 41;    -   an optimum orientation calculation module 43 which calculates        the optimum orientation Θopt for each pair of luminance mappings        CLI, CLR generated in real-time by the cartographic module 40        (in other words the optimum orientation at the current time        point) and also for each pair of predictive mappings CLIP, CLRP        originating from the predictive calculation module 42 (in other        words the optimum orientations for future time points);    -   an optimum orientation evolution module 44 which recovers all        the optimum orientations originating from the optimum        orientation calculation module 43 in order to establish the        evolution of the optimum orientation, and therefore forecast and        anticipate the optimum orientation changes;    -   a module 45 for parametrizing the solar module 1 which comprises        parameters related to the displacement speed of the actuation        system 6 (and therefore to the speed necessary for an        orientation change), parameters related to the energy        consumption necessary to the actuation system 6 for an        orientation change, parameters related to the solar energy        production generated by the faces 31, 32 of the photovoltaic        device 3 according to the solar luminance received on each face        31, 32, and parameters related to a wear rate of the mechanical        members of the solar tracker 2 loaded during a change of the        orientation of the solar module 1, these parameters being in        particular dependent of the angular difference between the start        and the end of the orientation change;    -   an astronomical calculation module 46 which calculates in        real-time the position of the Sun, and therefore the direct        orientation defined by the direction of the direct solar        radiation at the level of the solar module 1;    -   a servo-control module 47 which calculates the servo-control of        the orientation of the solar module 1, according to the        evolution of the optimum orientation originating from the module        44, the different parameters originating from the module 45 and        the direct orientation originating from the module 46, where        this servo-control module 47 outputs an orientation setpoint        toward the actuation system 6 in order to pilot changes of the        orientation of the solar module 1, in other words of the        platform 22 of the solar tracker 2.

It should be noted that this control unit 4 may be specific to the solarmodule 1, or shared between several solar modules, and preferablybetween several solar trackers arranged in line (extending from north tosouth) within linear solar plants.

In the two embodiments illustrated in FIGS. 3a and 3b (first embodiment)and in FIG. 4 (second embodiment), the measuring system 5 comprises aspherical-dome shaped support 53 a for the first embodiment or acircular-ring shaped support 53 b for the second embodiment.

In each embodiment, the support 53 a, 53 b supports photosensitivesensors 54, 55, in particular pyranometric-type sensors, with upperphotosensitive sensors 54 on the top (facing the sky) and lowerphotosensitive sensors 55 on the bottom (facing the ground); thesephotosensitive sensors 54, 55 consist in particular of pyranometric-typesensors.

The upper photosensitive sensors 54 form, together with the top portionof the concerned support 53 a, 53 b, the upper measuring device 51,whereas the lower photosensitive sensors 55 form, together with thebottom portion of the concerned support 53 a, 53 b, the lower measuringdevice 52.

The photosensitive sensors 54, 55 are distributed according to severalelevation angles called ΘSi for the upper photosensitive sensors 54 andΘNk for the lower photosensitive sensors 55; these elevation angles ΘSi,ΘNk being measured with respect to the vertical axis Z in the plane (Y,Z), the reference frame (X, Y, Z) being centered on the center O of thespherical dome 53 a or the center O of the circular ring 53 b; theseelevation angles ΘSi, ΘNi being therefore to be matched with theorientation of the solar module 1.

In general, the photosensitive sensors 54, 55 are positioned alongseveral strips (or rows) distributed according to several elevationangles ΘSi, ΘNk. These elevation angles ΘSi, ΘNk are also shown in FIG.6. The strips are distributed between upper strips BSi which compriseone or several upper photosensitive sensor(s) 54, and lower strips BNkwhich comprise one or several lower photosensitive sensor(s) 55.

In the first embodiment, on each strip lie one or several photosensitivesensor(s) 54, 55. In the case of a strip with several photosensitivesensors 54, 55, the photosensitive sensors 54, 55 of the same strip aredistributed according to several azimuth angles called RSj for the upperphotosensitive sensors 54 and RNm for the lower photosensitive sensors55; these azimuth angles RSj, RNm being measured with respect to thevertical axis Z in the plane (X, Z). Thus, besides being distributedaccording to the strips at different elevation angles ΘSi, ΘNk, thephotosensitive sensors 54, 55 are also distributed according to columnsat different azimuth angles RSj, RNm. These azimuth angles RSj, RNm areshown in FIG. 6. The columns are distributed between upper columns CSiwhich comprise one or several upper photosensitive sensor(s) 54, andlower columns CNm which comprise one or several lower photosensitivesensor(s) 55.

In the second embodiment, on each strip lies one single photosensitivesensor 54 or 55, such that there is only one single upper column and onesingle lower column.

In FIG. 6, in an example of a first measuring system 5, the upperphotosensitive sensors 54 are distributed according to four upper stripsBS1, BS2, BS3, BS4 which are associated to four elevation angles ΘS1,ΘS2, ΘS3, ΘS4, and according to four upper columns CS1, CS2, CS3, CS4which are associated to four azimuth angles RS1, RS2, RS3, RS4, and thelower photosensitive sensors 55 are distributed according to four lowerstrips BN1, BN2, BN3, BN4 which are associated to four elevation anglesΘN1, ΘN2, ΘN3, ΘN4, and according to four lower columns CN1, CN2, CN3,CN4 which are associated to four azimuth angles RN1, RN2, RN3, RN4.

In general, the more the measuring system 5 comprises photosensitivesensors 54, 55, and in particular the more the observation system 2comprises strips of photosensitive sensors 54, 55, and the better willbe the resolution and the angular accuracy.

These photosensitive sensors 54, 55 may be of the same technology as thefaces 31, 32 associated to the photovoltaic device 3 in order to enablethe application of a weighting dependent of the useful wavelength rangeof the faces 31, 32. Preferably, these photosensitive sensors 54, 55will undergo a prior calibration in order to obtain a better accuracy.

With the first measuring system 5, by recovering the measurements of theluminosity of each photosensitive sensor 54, 55 and knowing theelevation angles ΘSk, ΘNk of the different strips and the azimuth anglesRSj, RNm of the different columns, the cartographic module 40 converts ameasurement performed by the measuring system 5 into a pair of mappingscomprising an incident luminance mapping CLI (obtained with themeasurements originating from the upper photosensitive sensors 54) and areflected luminance mapping CLR (obtained with the measurementsoriginating from the lower photosensitive sensors 55).

Beforehand, the cartographic module 40 implements a frequency weightingapplied on the measurements performed by the photosensitive sensors 54,55; this frequency weighting consisting in applying a frequency filteron these measurements which is dependent of both the frequency responseof the photosensitive sensors 54, 55 and the useful frequency band (orspectral response) of the photovoltaic cells of the photovoltaic device3.

Afterwards, the cartographic module 40 implements a possible processingconsisting in correcting the measurements from defects or parasiticnoises. Then, the cartographic module 40 implements a calculation of thedistribution of the solar luminance (by matching the measurements of thephotosensitive sensors 54, 55 with their coordinates in the space ordirectly with their respective elevation angles) in order to generate araw incident luminance mapping and a raw reflected luminance mapping,each forming a solar luminance map (or matrix) distributed according toseveral strips associated respectively to different elevation anglesΘSi, ΘNk and, where appropriate, according to several columns associatedrespectively to different azimuth angles RSj, RNm.

Finally, the cartographic module 40 applies on each raw mapping aspecific coefficient dependent of the variation of the sensitivity ofthe photosensitive sensors 54, 55, in order to generate the incidentluminance mapping CLI and the reflected luminance mapping CLR which willbe exploited to establish the optimum orientation. Indeed, themagnitudes (or luminosities) of the measurements delivered by thephotosensitive sensors 54, 55 are proportionally related to the valuesof the (incident or reflected) solar radiation, so that thesecoefficients take into account these proportionalities depending on thevariations of sensitivity of the respective photosensitive sensors 54,55.

The incident luminance mapping CLI forms a solar luminance map (ormatrix) distributed according to:

-   -   several higher strips 50S(i) (i being an integer) established        according to a first direction parallel to the axis of rotation        A (and therefore parallel to the axis X) and associated        respectively to different elevation angles ΘSi, so that each        strip 50S(i) corresponds to an elevation angle ΘSi (each strip        50S(i) of the mapping CLI being associated to a strip BSi of the        measuring system 5); and    -   several upper columns 51S(j) (j being an integer) established        according to a second direction horizontal and orthogonal to the        axis of rotation A (and therefore parallel to the axis Y) and        associated respectively to different azimuth angles RSj (each        column 51S(j) of the mapping CLI being associated to a column        CSj of the measuring system 5).

Thus, the incident luminance mapping CLI comprises N cells (whereN=[i×j]), and to each cell corresponds one (absolute or relative) solarluminance value LumS(i,j). It is possible that some cells are empty,because the strips BSi do not necessarily comprise the same number ofupper photosensitive sensors 54, and in this case the solar luminancevalue LumS(i,j) is zero for an empty cell.

In the example of FIG. 5, the incident luminance mapping CLI comprisesfive strips 50S(1), . . . , 50S(5) and seven columns 51S(1), . . . ,51S(7), and the solar luminance values are expressed as relativepercentages.

The reflected luminance mapping CLR forms a solar luminance map (ormatrix) distributed according:

-   -   several lower strips 50N(k) (k being an integer) established        according to a first direction parallel to the axis of rotation        A (and therefore parallel to the axis X) and associated        respectively to different elevation angles ΘNk, so that each        strip 50N(k) corresponds to an elevation angle ΘNk (each strip        50N(k) of the mapping CLR being associated to a strip BNk of the        measuring system 5); and    -   several lower columns 51N(m) (m being an integer) established        according to a second direction horizontal and orthogonal to the        axis of rotation A (and therefore parallel to the axis Y) and        associated respectively to different azimuth angles RNm (each        column 51N(m) of the mapping CLR being associated to a column        CNm of the measuring system 5). Thus, the reflected luminance        mapping CLR comprises P cells (where P=[k×m]), and to each cell        corresponds one (absolute or relative) solar luminance value        LumN(k,m). It is possible that some cells are empty, because the        strips BNk do not necessarily comprise the same number of lower        photosensitive sensors 55, and in this case the solar luminance        value LumN(k,m) is zero for an empty cell.

In the example of FIG. 5, the reflected luminance mapping CLR comprisesfive strips 50N(1), . . . , 50N(5) and seven columns 51N(1), 51N(7), andthe solar luminance values are expressed as relative percentages.

From such a pair of mappings CLI, CLR, the optimum orientationcalculation module 43 implements a calculation based on these mappingsCLI, CLR to extract an optimum orientation Θopt which corresponds to anelevation angle associated to a maximum solar illuminance on the twofaces 31, 32 of the photovoltaic device 3.

For this calculation, and referring to FIGS. 5 and 6, the optimumorientation calculation module 43 implements a succession of substeps.This succession of substeps constitutes a calculation or algorithmexample, and the invention would not, of course, be limited to thisexample.

At a first substep, the optimum inclination angle calculation module 43calculates, for each strip 50S(i) of the incident luminance mapping CLI,an equivalent luminance value LeqS(i) from the set of luminance valuesLumS(i,j) taken in the strip 50S(i). For each strip 50S(i), theequivalent luminance value LeqS(i) of the strip 50S(i) is a function ofthe luminance values LumS(i,j) taken in the strip 50(i) and of theazimuth angles RSj of the different columns 51S(j) according to thefollowing formula (referring to FIG. 6):

${Leq{S(i)}} = {\sum\limits_{j}{Lum{S\left( {i,j} \right)} \times \cos\;{RSj}}}$

Thus, we obtain a matrix MLeqS of the equivalent luminance valuesLeqS(i) associated to the different strips 50S(i).

Similarly, the optimum inclination angle calculation module 43calculates, for each strip 50N(k) of the reflected luminance mappingCLR, an equivalent luminance value LeqN(k) from the set of luminancevalues LumN(k,m) taken in the strip 50N(k). For each strip 50N(k), theequivalent luminance value LeqS(i) of the strip 50N(k) is a function ofthe luminance values LumN(k,m) taken in the strip 50N(k) and of theazimuth angles RSm of the different columns 51N(m) according to thefollowing formula (referring to FIG. 6):

${Leq{N(k)}} = {\sum\limits_{jm}{Lum{N\left( {k,m} \right)} \times \cos\;{RNm}}}$

Thus, we obtain a matrix MLeqN of the equivalent luminance valuesLeqN(k) associated to the different strips 50N(k).

At a second substep, the optimum orientation calculation module 43calculates, for several theoretical elevation angles Θth, a valueLperc(Θth) of the luminance perceived by the faces 31, 32 of the solarmodule 1 from the equivalent luminance values LeqS(i) and LeqN(k)calculated for all strips at the first substep, and from the angulardifferences between the theoretical elevation angles Θth and theelevation angles ΘSi, ΘNk associated to the strips, according to thefollowing formula (referring to FIG. 6):

${Lperc}{\left( {\theta th} \right) = {{\sum\limits_{i}{Leq{{S(i)} \cdot {\cos\left( {{\theta\;{Si}} - {\theta\;{th}}} \right)} \cdot {p(i)}}}} + {\sum\limits_{k}{Leq{{N(k)} \cdot {\cos\left( {{\theta\;{Nk}} - {\theta\;{th}}} \right)} \cdot {p(k)}}}}}}$

Where p(i)=1 if abs(ΘSi-Θth)<90 degrees, and p(i)=0 otherwise;

and p(k)=1 if abs(ΘNk-Θth)<90 degrees, and p(k)=0 otherwise.

The coefficients p(i), p(k) take into account that, beyond an angulardifference of 90 degrees, the radiation is not received by thecorresponding photosensitive sensor(s) 54, 55.

Thus, we obtain a curve of the variation of the perceived luminancevalue Lperc(Θth) as a function of the theoretical elevation angle Θth.

At a last substep, the optimum orientation calculation module 43 retainsthe optimum orientation Θopt as being the theoretical elevation angleΘth associated to a maximum of the perceived luminance value Lperc(Θth).

In the case where the measuring system 5 is in accordance with thesecond embodiment, the mappings CLI, CLR are equivalent to the matricesMLeqS and MLeqN, so that the calculations implemented by the optimumorientation calculation module 43 starts at the second substep.

It should be noted that, in a non-illustrated variant, the two measuringdevices 51, 52 are made in the form of two cameras, in particularhemispherical type cameras, arranged back to each other, with an uppercamera turned toward the sky in order to extract images of the sky andmeasure the distribution of the incident solar luminance, and a lowercamera turned toward the ground in order to extract images of the groundand measure the distribution of the reflected solar luminance.Advantageously, each camera is configured to take images within aspectral width sufficient for the technology of the photovoltaic cellsof the faces 31, 32 of the photovoltaic device 3. Each camera delivers araw image, respectively of the sky and of the ground, which is deliveredafterwards to the cartographic module 40 for converting these two rawimages into mappings CLI, CLR equivalent to those described hereinabove,after a succession of image processing steps starting from the rawimages until the mappings CLI, CLR:

-   -   a frequency weighting step;    -   a processing step consisting in correcting the defects on the        images after weighting (noise suppression processing, blooming        processing, saturation processing, . . . );    -   calculation (either pixel-by-pixel, or area-by-area where each        area comprises several pixels) of the distribution of the solar        luminance;    -   application on each processed image of a specific coefficient        dependent of the variation of the sensitivity of the concerned        camera.

The predictive calculation module 42 calculates predictive incidentluminance mappings CLIP and predictive reflected luminance mappings CLRPfor future time points (t+nP), where n is a non-zero integer and P theperiod of the observation carried out periodically and repetitively bythe measuring system 5. These predictive mappings CLIP, CLRP areestablished on the basis of the mappings CLI, CLR generated in real-timeby the cartographic module 40 and on the basis of the past mappings CLI,CLR archived in the archiving module 41.

From the successive incident luminance mappings CLI, the predictivecalculation module 42 has access, more or less accurately, to alocalization of the clouds, as well as their dimensions, theirdirections of displacement and their displacement speeds. Thus, thepredictive calculation module 42 can implement a predictive calculationof the position of the clouds at future time points.

The predictive calculation is based on the consideration of the pastevolution of the distribution of the incident solar luminance, betweenseveral past time points and the current time point, and in particularthe evolution of the distribution of the incident solar luminance and ofthe speed of evolution of the incident solar luminance.

This predictive calculation may be based on a sliding time window, thatis to say a window comprising a predefined number of the last pastmappings.

This predictive calculation is used to establish short-term predictivemappings CLIP, CLRP (or mapping forecasts). As a non-limiting example,the short-term notion covers calculations over a future time period ofat most ten to thirty minutes, or at most one to two hours. Of course,it is possible to consider providing for predictive calculations over alonger term.

The algorithm implemented for such a predictive calculation may possiblyintegrate improvements such as:

-   -   the consideration of the forecast errors in order to improve the        future forecasts (indeed, it is possible to compare the current        mappings with the cartographic forecasts performed earlier, in        order to draw out lessons regarding the predictive calculation        and improve it);    -   recognize the cloud types according to the incident luminance        mappings CLI thanks to a database and/or thanks to analyses or        readings performed in the past, so as to allow making forecasts        over a longer term depending on the types of clouds.

The algorithm implemented for such a predictive calculation may alsotake into account the evolution of the position of the Sun in the sky,in particular if the predictive calculation is performed for future timepoints far enough (for example beyond 30 minutes) for the change of theposition of the Sun having any influence on the evolution of theincident or reflected solar luminance. This consideration of theposition of the Sun in the predictive calculation is illustrated by theconnecting arrow in dashed line in FIG. 8 between the predictivecalculation module 42 and the astronomical calculation module 46.

As shown in FIG. 7, the predictive calculation module 42 establishespredictive mappings CLIP, CLRP, and to each pair of predictive mappingsCLIP, CLRP is associated a predictive optimum orientation Θoptcalculated by the optimum orientation calculation module 43, accordingto the same previously-described calculation method.

Thus, the optimum orientation evolution module 44 recovers all theoptimum orientations (those of the past mappings CLI, CLR, those of thecurrent mappings CLI, CLR, and those of the predictive mappings CLIP,CLRP) and establishes a future evolution of the optimum orientationΘopt, thereby enabling forecast and anticipation of the optimumorientation changes.

Finally, the servo-control module 47 servo-controls the orientation ofthe solar module 1 according to the past and future evolution of theoptimum orientation Θopt, and also according to the energy consumptionCons necessary to modify the orientation of the solar module 1, therotational displacement speed of the solar module 1, and thesupplemental solar energy production Prod obtained with an orientationchange.

Referring to FIGS. 9 and 10, the servo-control module 47 is based on thefuture evolution of the optimum orientation Θopt (first curve startingfrom the top).

In the given example, the predictive optimum orientation Θopt changes invalue so as to reach a target value Θc, for example because of aforecast of the passage of a cloud in front of the Sun, from the futuretime point t1 until the future time point t2, before returning back toits initial value.

The servo-control module 47 establishes a potential scenario duringwhich the orientation Θ of the solar module 1 is modified starting froma current orientation Θp until reaching the target optimum orientationΘc, in order to follow the forecast of the evolution of the optimumorientation.

In the given example, the scenario consists in servo-controlling theorientation Θ on the first curve, and this servo-control depends on therotational displacement speed of the solar module 1, in order to obtaina second curve of the evolution of the orientation Θ of the solar module1 during the orientation change of the scenario. Indeed, the solarmodule 1 presents a displacement time necessary to be able to reach thetarget optimum orientation Θc.

Thanks to the predictive calculation, the displacement of the solarmodule 1 is anticipated, in this instance by starting earlier at thetime point t10 (anterior to t1) until reaching the target value Θc att11 (subsequent to t1), and then by starting in an anticipated mannerthe return at the time point t11 (anterior to t2) until returning backto the current orientation Θp at the time point t13 (subsequent to t2).

The servo-control module 47 determines the evolution of the energyconsumption Cons necessary to modify the orientation of the solar module1 according to the second curve, in order to obtain a third curve of theevolution of this energy consumption Cons; the solar module 1 consumingduring the orientation change phases, between the time points t10 andt11 and then between the time points t12 and t13.

The servo-control module 47 determines the evolution of the expectedsupplemental production Prod (or production gain) by following thesecond curve of the evolution of the orientation Θ rather than remainingat the current orientation Θp, in order to obtain a fourth curve of theevolution of this production Prod. Hence, this supplemental productionProd corresponds to the expected production gain if the scenario isfollowed rather than remaining at the initial or current situation onthe current orientation Θp.

In the given example, the production Prod is negative between the timepoints t10 and t1 and between the time points t2 and t13 whichcorrespond to periods where the orientation Θ departs from the optimumorientation Θopt, and the production Prod is positive between the timepoints t1 and t2 which correspond to a period where the orientation Θapproaches and even becomes equal to the optimum orientation Θopt.

The servo-control module 47 determines the evolution of the expectedenergy yield Rend based on the difference between the energy productionProd and consumption Cons, resulting in a fifth curve corresponding tothe difference between the fourth curve and the third curve, in otherwords Rend=Prod−Cons.

In the given example, the yield Rend is negative between the time pointst10 and t1 and between the time points t2 and t13, and the yield Rend ispositive between the time points t1 and t2.

Finally, the servo-control module 47 follows the scenario (in otherwords servo-controls the solar module according to the second curve) ifthe energy yield is globally positive for the scenario, otherwise theorientation of the solar module 1 is maintained at the currentorientation Θp.

The overall energy yield is established by studying the yield over theentire period of the scenario.

In the example of FIG. 9, the overall yield is negative, because the sumof the surfaces Srn where the yield is negative (between t10 and t1 andbetween t2 and t13) is larger than the surface Srp where the yield ispositive (between t1 and t2). For example, the example of FIG. 11corresponds to a situation where the predictive passage time(corresponding to the interval [t2−t1]) of a cloud in front of the Sunis too short in comparison with the time necessary for an orientationchange (corresponding to the interval [t1−t10] or [t13−t2]). In theexample of FIG. 10, the overall yield is positive, because the sum ofthe surfaces Srn where the yield is negative (between t10 and t1 andbetween t2 and t13) is smaller than the surface Srp where the yield ispositive (between t1 and t2). For example, the example of FIG. 10corresponds to a situation where the predictive passage time(corresponding to the interval [t2−t1]) of a cloud in front of the Sunis long in comparison with the time necessary for an orientation change(corresponding to the interval [t1−t10] or [t13−t2])

Thus, in the example of FIG. 9, the servo-control module 47 does notfollow the scenario and maintains the orientation at the current valueΘp, whereas in the example of FIG. 10, the servo-control module 47follows the scenario and ensures a servo-control of the inclinationangle according to the second curve.

Referring to FIGS. 1(a) and 1(b), the method in accordance with theinvention is implemented in FIG. 1(b) with an orientation of the solarmodule 1 on an optimum orientation Θopt distinct from the directorientation Θdir (orientation on the direct radiation facing the SunSO), whereas in FIG. 1(a) is implemented an orientation of the solarmodule 1 on the direct orientation Θdir. With the presence of clouds NUin front of the Sun SO, the direct incident solar radiation Rdir islower than the diffuse incident solar radiation Rdif, so that theservo-control on the direct orientation Θdir procures a lower yield thanthe servo-control on the optimum orientation Θopt established thanks tothe method (which takes into account the diffuse radiation Rdif and alsothe albedo radiation Ralb), so that the method enables an increase ofthe energy production by the solar module 1.

Referring to FIGS. 2(a) and 2(b), the method in accordance with theinvention is implemented in FIG. 2(b) with an orientation of the solarmodule 1 on an optimum orientation Θopt distinct from the directorientation Θdir, whereas in FIG. 2(a) is implemented an orientation ofthe solar module 1 on the direct orientation Θdir. With the presence ofa high albedo solar radiation Ralb due to a ground SOL having a highreflectance, the servo-control on the direct orientation Θdir turns outto procure a lower yield than the servo-control on the optimumorientation Θopt established thanks to the method which takes intoaccount the high albedo radiation Ralb, because the servo-control on thedirect orientation Θdir will limit the consideration of the albedoradiation Ralb.

Of course, the example of implementation mentioned hereinabove is notlimiting and other improvements and details may be added to the solartracker according to the invention, nevertheless without departing fromthe scope of the invention where other types of fixed structure orplatform may be for example carried out.

The invention claimed is:
 1. A method for controlling an orientation ofa solar module supported by a solar tracker, the solar module includinga photovoltaic device and having a photoactive upper face facing the skyand provided with photovoltaic cells and a photoactive lower face facingthe ground and provided with photovoltaic cells, the method comprising:measuring a distribution of incident radiation an upper face of thephotovoltaic device at several elevation angles corresponding to severalorientations of the solar module; measuring a distribution of reflectedradiation a lower face of the photovoltaic device at several elevationangles corresponding to several orientations of the solar module aboutthe axis of rotation; determining past optimum orientations of the solarmodule based on past measurements of a distribution of incidentradiation and of a distribution of reflected radiation; forecastingfuture evolutions of the distributions of the incident and reflectedradiation based on the past measurements; calculating future evolutionof the optimum orientation based on the future evolutions of thedistributions; and controlling the orientation of the solar module tothe optimum orientation based on the past optimum orientations and thefuture evolution of the optimum orientation.
 2. The method according toclaim 1, wherein the forecasting of the future evolutions of thedistribution of the incident radiation and of the distribution of thereflected radiation is based on a weather forecast calculation in alocation area of the solar module.
 3. The method according to claim 1,wherein the determination of the past optimum orientations of the solarmodule is based at least partially on a research, in the distribution ofthe incident radiation and in the distribution of the reflectedradiation, of an elevation angle associated with a maximum solarilluminance on the two faces of the photovoltaic device.
 4. The methodaccording to claim 1, wherein the determination of the past optimumorientations of the solar module is based at least partially on aresearch, in the distribution of the incident radiation and in thedistribution of the reflected radiation, of an elevation angleassociated with a maximum energy production of the solar module.
 5. Themethod according to claim 3, wherein the determination of the pastoptimum orientations of the solar tracker is also based on the at leastone of: an electrical energy consumption necessary to modify theorientation of the solar module; a wear rate of mechanical members ofthe solar tracker loaded during a change of the orientation of the solarmodule; an angular speed of the solar tracker during a change of theorientation of the solar module; or an angular displacement of the solartracker between a minimum orientation and a maximum orientation.
 6. Themethod according to claim 1, wherein: when measuring the distribution ofthe incident radiation is implemented a frequency weighting dependent ofa frequency response of the photovoltaic cells of the upper face of thephotovoltaic device; and when measuring the distribution of thereflected radiation is implemented a frequency weighting dependent of afrequency response of the photovoltaic cells of the lower face of thephotovoltaic device.
 7. The method according to claim 1, whereindetermining an optimum orientation includes: converting the distributionof the incident radiation into an incident luminance mapping defining adistribution of luminance values (LumS(i,j)) according to upper strips,established according to a first direction parallel to an axis ofrotation, and according to columns called upper columns, establishedaccording to a second direction orthogonal to the first direction, whereeach upper strip is associated to an elevation angle and each uppercolumn is associated to an azimuth angle; converting the distribution ofthe reflected radiation into a reflected luminance mapping defining adistribution of luminance values (LumN(k,m)) according to lower stripsaccording to the first direction, and according to lower columnsaccording to the second direction, where each lower strip is associatedwith an elevation angle and each lower column is associated with anazimuth angle; calculating, for each upper and lower strip, of anequivalent luminance value from a set of luminance values taken in aconsidered strip; calculating, for several theoretical elevation anglescorresponding to several orientations of the solar module, of luminancevalues perceived by the two faces of the photovoltaic device from theequivalent luminance values calculated for the upper and lower stripsand from angular differences between the theoretical elevation anglesand the elevation angles associated with the upper and lower strips; anddetermining a theoretical elevation angle associated with a maximum of aperceived luminance value and selection of said theoretical elevationangle as the optimum orientation.
 8. The method according to claim 1,wherein the the distribution of the incident radiation and of thedistribution of the reflected radiation are carried out by an imagecapturing device which ensures a capture of images of the sky formeasuring the distribution of the incident radiation and a capture ofimages of the ground for establishing the measurement of thedistribution of the reflected radiation.
 9. The method according toclaim 1, wherein the distribution of the incident radiation and of thedistribution of the reflected solar luminance radiation are carried outby a measuring system comprising several photosensitive sensors, inparticular pyranometric-type sensors, with an upper measuring devicehaving upper photosensitive sensors distributed facing the sky formeasuring the distribution of the incident radiation and a lowermeasuring device having lower photosensitive sensors distributed facingthe ground for measuring the distribution of the reflected solarluminance radiation.
 10. The method according to claim 1, whereincontrolling the orientation of the solar module is carried out accordingto an energy consumption necessary to modify the orientation of thesolar module.
 11. The controlling method according to claim 10, furthercomprising establishing a potential scenario during which theorientation of the solar module is modified starting from a currentorientation until reaching an optimum orientation, and to the potentialscenario are associated calculations of: an evolution of the orientationof the solar module starting from the current orientation until reachingthe optimum orientation, this evolution depending on a rotationaldisplacement speed of the solar module; an evolution of the energyconsumption necessary to modify the orientation of the solar module; anevolution of a supplemental solar energy production expected with suchan orientation change; an evolution of an expected energy yield based ona difference between the supplemental solar energy production and theenergy consumption; and afterwards, the orientation of the solar moduleis servo-controlled on the optimum orientation if the expected energyyield is globally positive for the potential scenario, otherwise theorientation of the solar tracker is maintained at the currentorientation.